Resumo -A partir das indicações do último relatório do IPCC (International Pannel of Climatic Change), foram feitas várias simulações e avaliados os impactos que um aumento na temperatura média do ar de 1 o C, 3 o C e 5,8 o C e um incremento de 15% na precipitação pluvial teriam na potencialidade da cafeicultura brasileira, definida pelo atual zoneamento agroclimático do café (Coffea arábica L.) nos Estados de Goiás, Minas Gerais, São Paulo e Paraná. Os resultados indicaram uma redução de área apta para a cultura superior a 95% em Goiás, Minas Gerais e São Paulo, e de 75% no Paraná, no caso de um aumento na temperatura de 5,8 o C. Esses resultados são válidos se mantidas as atuais características genéticas e fisiológicas das cultivares de café arábica utilizadas no Brasil, que têm como limite de tolerância temperaturas médias anuais entre 18 o C e 23 o C.Termos para indexação: Coffea arabica, zoneamento agrícola, aumento de temperatura. Climatic changes impact in agroclimatic zonning of coffee in BrazilAbstract -According to the last report of the Intergovernmental Panel on Climate Change (IPCC), the global temperature is supposed to increase 1°C to 5.8°C and the rainfall 15% in the Tropical area. This paper analyses the effect that these possible scenarios would have in the agroclimatic zoning of the arabic coffee (Coffea arabica L.) main plantation areas in Brazil. The results indicated a reduction of suitable areas greater than 95% in Goiás, Minas Gerais and São Paulo and about 75% for Paraná in the case of a temperature increase of 5.8 o C. These results presume that all the physiological characteristics of the crop will be the same for the varieties analyzed and that the ideal climatic condition for economic development is mean annual temperatures between 18 o C and 23 o C.Index terms: climatic change , agroclimatic zoning, Coffea arabica. IntroduçãoA problemática das mudanças climáticas globais levou a Organização Meteorológica Mundial (OMM) e a UNEP (United Nations Environment Programme) a criarem o IPCC (Intergovernmental Panel on Climate Change) em 1988. Segundo o IPCC, no século XX, houve um aumento de 0,65 o C na média da temperatura global, sendo este mais pronunciado na década de 90. Quanto à precipitação, o aumento variou de 0,2% a 0,3% na região tropical, compreendida entre 10 o de latitude Norte e 10 o de latitude Sul. As causas dessas variações podem ser de ordem natural ou antropogênica, ou uma soma das duas (IPCC, 2004).Por meio de modelos matemáticos baseados em dados registrados dos oceanos, biosfera e atmosfera, está previsto um aumento entre 1,4 o C e 5,8ºC na temperatura média global até o final do século XXI (IPCC, 2004). A magnitudes de tal previsão é ainda incerta, pois pouco se sabe sobre os processos de trocas de calor, de carbono e de radiação entre os diversos setores do sistema Terra. Segundo Kalnay & Cai (2003), a temperatura poderá subir em até 0,088 o C por década, chegando próximo da situação mais otimista indicada no relatório do IPCC.Com o aquecimento global, em um futuro pr...

Abstract. In this paper we calculated soil carbon stocks in Brazil studying 17 paired sites where soil stocks were determined in native vegetation, pastures and crop-livestock systems (CPS), and in other regional samplings encompassing more than 100 pasture soils, from 6.58 to 31.53 • S, involving three major Brazilian biomes: Cerrado, Atlantic Forest, and the Pampa. The average native vegetation soil carbon stocks at 10, 30 and 60 cm soil depth were equal to approximately 29, 64, and 92 Mg ha −1 , respectively. In the paired sites, carbon losses of 7.5 Mg ha −1 and 11.6 Mg ha −1 in CPS systems were observed at 10 cm and 30 cm soil depths, respectively. In pasture soils, carbon losses were similar and equal to 7.5 Mg ha −1 and 11.0 Mg ha −1 at 10 cm and 30 cm soil depths, respectively. Differences at 60 cm soil depth were not significantly different between land uses. The average soil δ 13 C under native vegetation at 10 and 30 cm depth were equal to −25.4 ‰ and −24.0 ‰, increasing to −19.6 ‰ and −17.7 ‰ in CPS, and to −18.9 ‰, and −18.3 ‰ in pasture soils, respectively; indicating an increasing contribution of C 4 carbon in these agrosystems. In the regional survey of pasture soils, the soil carbon stock at 30 cm was equal to approximately 51 Mg ha −1 , with an average δ 13 C value of −19.6 ‰. Key controllers of soil carbon stock in pasture sites were sand content and mean annual temperature. Collectively, both could explain approximately half of the variance of soil carbon stocks. When pasture soil carbon stocks were compared with the average soil carbon stocks of native vegetation estimated for Brazilian biomes and soil types by Bernoux et al. (2002) there was a carbon gain of 6.7 Mg ha −1 , which is equivalent to a carbon gain of 15 % compared to the carbon soil stock of the native vegetation. The findings of this study are consistent with differences found between regional comparisons like our pasture sites and plot-level paired study sites in estimating soil carbon stocks changes due to land use changes.

Agriculture appears to be one of the human activities most vulnerable to climatic changes due to its large dependence on environmental conditions. However, the diversity of Brazilian environmental conditions could be of great advantage to adapting this sector to new climatic conditions, which should be assessed as in this study on shifting Arabica coffee cultivation to the extreme south of the country. The methodology applied is the same the one used to define climatic risks in current productive regions of Brazil and their vulnerability to climatic change predicted by IPCC reports. The basic climatic parameters applied were frost probability and annual average temperature, since annual water deficit did not prove to be a restricting factor for Arabica coffee cultivation in the study area. The climatic conditions suitable for coffee production are: annual average temperature between 18 • C and 22 • C, annual water deficit less than 100 mm and frost probability (risk of lowest annual temperature less than 1 • C) less than 25%. An area is said to have "low climatic risks" for coffee production when these three climatic conditions are met. Current climatic conditions were used and simulations of four temperature increases between 1 • C and 4 • C were also performed. The results indicated a substantial increase in the size of low climatic risks areas for the production of Arabica coffee in the extreme south of Brazil, mainly for mean temperature increases of 3 • C in

Abstract. In this paper, soil carbon, nitrogen and phosphorus concentrations and stocks were investigated in agricultural and natural areas in 17 plot-level paired sites and in a regional survey encompassing more than 100 pasture soils In the paired sites, elemental soil concentrations and stocks were determined in native vegetation (forests and savannas), pastures and crop-livestock systems (CPSs). Nutrient stocks were calculated for the soil depth intervals 0-10, 0-30, and 0-60 cm for the paired sites and 0-10, and 0-30 cm for the pasture regional survey by sum stocks obtained in each sampling intervals (0-5, 5-10, 10-20, 20-30, 30-40, 40-60 cm). Overall, there were significant differences in soil element concentrations and ratios between different land uses, especially in the surface soil layers. Carbon and nitrogen contents were lower, while phosphorus contents were higher in the pasture and CPS soils than in native vegetation soils. Additionally, soil stoichiometry has changed with changes in land use. The soil C : N ratio was lower in the native vegetation than in the pasture and CPS soils, and the carbon and nitrogen to available phosphorus ratio (P ME ) decreased from the native vegetation to the pasture to the CPS soils. In the plotlevel paired sites, the soil nitrogen stocks were lower in all depth intervals in pasture and in the CPS soils when compared with the native vegetation soils. On the other hand, the soil phosphorus stocks were higher in all depth intervals in agricultural soils when compared with the native vegetation soils. For the regional pasture survey, soil nitrogen and phosphorus stocks were lower in all soil intervals in pasture soils than in native vegetation soils. The nitrogen loss with cultivation observed here is in line with other studies and it seems to be a combination of decreasing organic matter inputs, in cases where crops replaced native forests, with an increase in soil organic matter decomposition that leads to a decrease in the long run. The main cause of the increase in soil phosphorus stocks in the CPS and pastures of the plot-level paired site seems to be linked to phosphorus fertilization by mineral and organics fertilizers. The findings of this paper illustrate that land-use changes that are currently common in Brazil alter soil concentrations, stocks and elemental ratios of carbon, nitrogen and phosphorus. These changes could have an impact on the subsequent vegetation, decreasing soil carbon and increasing nitrogen limitation but alleviating soil phosphorus deficiency.

Resumo -Este trabalho teve por objetivo avaliar um sistema de previsão de safra de soja para o Brasil, baseado em modelos empíricos regionalizados para estimativa da produtividade, a partir de um banco de dados de área cultivada em escala municipal, e de um sistema de monitoramento agrometeorológico de abrangência nacional. Forecast system of soybean crop yield for BrazilAbstract -The aim of this work was to evaluate a system to forecast soybean crop yield for Brazil, based on regional empirical models to assess crop yield, with data from a national database of soybean cropped area in municipal scale, and from an agrometeorological monitoring system covering all Brazilian States. The models incorporated the conceptual bases proposed by Doorenbos & Kassam, with empirical adjustments for each region of Brazil, considering the diverse potential yield of most used varieties and the regional differences in the soybean production systems. Cultivated area database from each State was structured with data from IBGE and Conab. Soybean yield was estimated for harvests from 2000/2001 to 2005/2006 and compared to Conab surveys. Statistical analysis using Test t point out that there is no significant difference between estimates and official data. Good fittings were gotten for region grouped yield data (R 2 ≥0.87), with higher deviations for harvest assessment of Rio Grande do Sul, Santa Catarina, Mato Grosso do Sul, Maranhão, Piauí and Bahia. In national scale, the highest observed deviation was 5.81% for the 2000/2001 harvest, and the smaller one was 0.62% for the 2005/2006 yield.